The present invention concerns the monitoring of the system margin of an integrated circuit. The technique presented herein may also be used to monitor the core temperature of the integrated circuit.
The propagation delay of signals in integrated circuits is affected by many factors. These include the voltage level of VCC, process variations in production of the integrated circuit, system variations (such as input and output capacitance to the integrated circuit) and temperature.
In order to assure that timing within an integrated circuit is adequate, a system margin for the integrated circuit is utilized. That is, rather than designing output signals of the integrated circuit to be available at the last possible instant, the integrated circuit is designed so that, under optimal operating conditions, the signals arrive at the destination early. This early arrival allows for delays introduced by adverse circumstances, such as a lowered VCC, an increase in temperature and unfavorable processing variations. Thus integrated circuits are generally designed to operate sufficiently even under non-optimal conditions.
However, the trend over time in designing integrated circuits is to continue to provide integrated circuits with lower VCC and faster operating frequency. It would be advantageous therefore for purchasers of integrated circuits to be able to measure the system margin built in by the manufacturer for the purpose of evaluation and possibly to adjust the operating parameters of the integrated circuit to, where desirable, change the system margin.
In addition, in many high performance integrated circuits, operation of the integrated circuit can result in the generation of a significant amount of heat. If the amount of heat is not limited or adequately dissipated, performance of the integrated circuit can be significantly impeded and/or circuitry within the integrated circuit can be destroyed.
In order to avoid overheating integrated circuits, the integrated circuits and the system containing the integrated circuits can be designed so that even under worst case operating conditions there will not be significant enough accumulation of heat to overheat the integrated circuit. However, this over design will result in integrated circuits which will have an overabundance of system margin and which will not perform optimally under normal operating conditions.
Alternatively, some way can be devised to try to determine the temperature of the integrated circuit. For instance, this could be done by measuring the temperature on the casing of the processor chip using a thermistor or similar technique. Alternatively, a software routine can be used to monitor operation of the integrated circuit, and based on past and current operations estimating the temperature of the integrated circuits. One problem with all these methods of monitoring temperature is that they are extremely inaccurate. Additionally, the added circuitry/software may be expensive to implement.